lifespan of CYA

[dbyang]

Earlier this summer, my pool was doing great, with swg set on 20%, fc at 3, cc at 0, cya at 25.

After returning from one week vacation, I found fc at 0,cc at 0.5, and cya at 0, and a little algae on side wall of one corner of the pool. I bumped the swg to 40% and started adding 7 lbs of cya over the course of last 2 weeks, now reading 25. In addition to swg, I am also adding 10% liquid chlorine about a quart/day. Still losing fc like crazy, still no cc, with minimal green algae at one corner of the pool. Starting to think it's algae, not the lack of cya, or maybe both. Should I slam now, or wait til I get the cya higher? The pool water is still clear, but not as sparkling as it used to be.

Last night fc was 2.5 after adding half gallon of chlorine, this morning fc down to 0.5, with the swg running.

In four years of having this pool, have never slammed before, never seen chlorine used so rapidly.

Second question: I have read that cya doesn't get used up. I have never drained the pool since initial startup. Get occassional dilution from rain, but I use the automated cover during the off-season, pumping off the rain water from the top of the pool cover. So where did the cya go? Is there a real lifespan to cya? Does it become ineffective with 4 years of age?

Thanks for any help.

dbyang

 

[JVTrain]

Re: lifespan of cya

CYA can go away VERY (emphasis on VERY) slowly. So much so that most folks will never notice it. However, if you do not adequately chlorinate your pool, under certain conditions which usually happens over winter when the pool is closed, the CYA can be consumed rapidly by a specific type of soil bacteria that may get into the pool. In this case, it is converted to ammonia. I doubt that's what's happening here. It's more likely that you're losing a small amount over time to splash out or an undetected leak.

That being said, having algae means you're not sanitizing properly and that could introduce conditions, though rare, where CYA might be decomposed.

Your primary concern right now is to SLAM the pool and get rid of the algae. SLAM Procedure
When starting your SLAM, adjust pH to near 7.2 as recommended. Then get CYA dissolving in a sock at a return. Enough to target 30 ppm for your pool using Pool Math
Then complete the SLAM. Follow it to the letter. Test and dose as often as practical and brush your pool, run auto cleaner if you have one.

While completing the SLAM, review the CYA/Chlorine Chart What is recommended for SWCG pool is a higher CYA level. Higher than the 25 you were using before. Notice the chart for SWCG pools goes from 60-80 ppm CYA. That's what you should adjust to AFTER completing the SLAM. It's a more economical use of the SWCG.

Also, adding your location to your profile so it shows up on your posts is helpful. Operating a pool in Utica, NY is different that operating one in Mesa, AZ.

 

[Richard320]

Re: lifespan of cya

How do you know the CYA is at zero? The testers can't read below 20. You might be at 18 or 15 and it reads as zero.

There's two problems going on: you're losing FC to both organics and sunlight. And once algae gets started, the SWG can't keep up with the demand and as the algae keeps growing, eventually all the FC disappears as soon as it hits the pool. 25 CYA is too low for a SWG. The thing was struggling to keep up with the demand because so much was being destroyed by the sun before the algae and obviously, it got overwhelmed.

Depending on pH and TA readings, you might want to use some dichlor shock for the first few doses of the Shock Level And Maintain process. That will quickly raise the CYA and the FC, but it will also lower pH and TA some. If it means you'll need to add Borax and Baking Soda, add FC and CYA separately. If you post a full set of test results, someone can advise you on that.

Raise CYA to 30 ish, SLAM the pool until you pass all three tests, and then raise CYA to 70ish and things should be smooth the remainder of the season.

 

[dbyang]

Re: lifespan of cya

OK, I added my location, Tallahassee, FL to my signature.

I was guessing that my initial cya was zero because with the cya tube up to the 20 mark, I still clearly see the black dot, without any cloudiness whatsoever.

I just had water tested at Pinch-a-Penny to double check my readings: FC 0.0, pH 7.5, TA 120ppm, CH 300 PPM Stabilizer 20ppm, salt 3500ppm. This is one hour after adding 1.5 gallons of 10% liquid hypochlorite. My CC reading was between 0.5 and 1.0, my FC reading also 0.0(swg still on at 40%).

I just bought 8 lbs. of Salinity shock (di-chloro...) The pool guy said I should not be using hypochlorite in a salt water pool. He said that interferes with the di-chloro.. that the swg produces. Is that true? He also recommended another 9.8 lbs of stabilizer.

I'm going to do bucket test before wasting too much chemicals.

 

[jblizzle]

Re: lifespan of cya

Your "pool guy" has no idea what he is talking about. It is fine to use bleach in a SWG pool. And an SWG does NOT produce di-chloro.

Do you realize that the dichlor is going to add CYA too? Have you calculated how much that 8 pounds is going to add to your pool?

What is the bucket test for?

 

[Leebo]

Re: lifespan of cya

Might I ask what test kit you are using?

 

[RobbieH]

Re: lifespan of cya

As Jason stated, sodium hypochlorite (bleach) absolutely does not interfere with dichlor or trichlor. Total rubbish. And, anyone that says an SWG creates dichlor is really ignorant (note, I did not say stupid). Just goes to show you, that pool store person has no idea what they are talking about, which is very common.

 

[dbyang]

Re: lifespan of cya

I am using tf-100 test kit.

Richard320 said dichloro adds to cya, but I don't know how much. And I am low on cya (20ppm).

The bucket test is a scaled down version of my pool, using 2.5gals instead of experimenting with my 25,000 gal pool. So I am adding 1/10,000 of the chemicals that I am planning to use in my pool, see what effect it has, before pouring all 8 lbs of dichlor in.

 

[RobbieH]

Re: lifespan of cya

Use PoolMath at the top of the page. Fill in all your pool specifics, then at the bottom there's a spot to calculate the effects of adding different things to your pool.

 

[jblizzle]

Re: lifespan of cya

I fail to see the importance of the bucket test. PoolMath with tell you exactly what the chemicals will do in your pool.

In your pool, each pound of Dichlor will add 2.7ppm FC and 2.4ppm CYA ... so that entire 8 pounds will only 21.6ppm of FC and 19.2ppm of CYA.
Since shock level is only 10ppm for you untill you add CYA ... you should only start with about 4 pounds and then maintain the correct shock FC level as the CYA rises.

Much simpler and cheaper to just add the stabilizer separately and use liquid chlorine.

 

[Leebo]

Re: lifespan of cya

I would suggest reading the ABC's of Pool Water Chemistry. You'll see just how far off the pool stores advice is.

 

[kimkats]

Re: lifespan of cya

I also live in Tallahassee and can tell you that Pinch a Pinny testing is NOT good!

I took a water sample to both PaP (Lake Jackson and by Florida Motor Sports) and got VERY different results and advice. The cheapest "fix" was $75 and the other was $158! Leslies by the mall was also off!

See I had already tested my water at home with my test kit I got from here. ALL of the levels were right in the middle of purrrfect. My water looked, smelled and felt great!

I have no idea where you CYA went. Is there ANY chance someone "helped" with your pool while you were gone? Could someone have dumped the water out by turning a valve or ????? Did you have yard people come by? Just throwing ideas out there.

This has been a weird year with the chlorine use and such. I was using more that last year at one point. Now it is back to normal. Never did figure out why. I just did a SLAM and moved on once my pool held chlorine.

I see brushing of your pool in your future as sell as buying lots of chlorine for your SLAM.

Good luck!

Kim

 

[dbyang]

Re: lifespan of cya

OK, so here is what I have done so far:

Day 1
5pm fc 0.0 added 4 lbs of dichlor and 1.25 gal of 10% hypochlorite (target fc 10)
8pm fc 3.5 added 1.25 gal of 10% hypochorite, ran out, pool store closed
Day 2
9am fc 1.0 added 2.5 gal of 10% hypochlorite (target fc 10.0 as per chart)
10am fc10.0 added 0.4 gal of 10% (target fc 12.0, assuming dichlor might have raised cya to 30)
11am fc 12.0 cya tested at 40ppm; added 1.0 gal of 10% (target fc 16 for cya of 40)

Keeping cover on pool in between additions of 10% to prevent sunshine degradation of CL. Also suspect that some algae may be on the underside of the cover, so trying to expose the cover to high level CL.

That's it for now.

 

[jblizzle]

Sounds like you are making progress

 

[RobbieH]

You don't have to buy hypochlorite at the pool store. Your local WalMart or grocery store has it on the shelves. Bleach. Plain bleach.

 

[tim5055]

You don't have to buy hypochlorite at the pool store. Your local WalMart or grocery store has it on the shelves. Bleach. Plain bleach.

While I agree with this, many do buy it at the pool store because in their location is is less expensive to buy there. You just need to run the numbers to compare the cost of equal ppm of chlorine.

Now, for me I just stick with 8.25% in my Stenner because I have the run time worked out to keep my FC where i want it. If there is a sale on 8.25% great, but I'm not switching to other percentages as it would require me playing with my Stenner again.

 

[RobbieH]

I was referring to the fact he stated he couldn't get more because the store was closed. I wouldn't hesitate to pay a little more to keep the SLAM process running.

 

[tim5055]

I was referring to the fact he stated he couldn't get more because the store was closed. I wouldn't hesitate to pay a little more to keep the SLAM process running.

Oops, sorry missed that.....

 

[dbyang]

update:

Day 1
5pm fc 0.0 added 4 lbs of dichlor and 1.25 gal of 10% hypochlorite (target fc 10)
8pm fc 3.5 added 1.25 gal of 10% hypochorite, ran out, pool store closed
Day 2
9am fc 1.0 added 2.5 gal of 10% hypochlorite (target fc 10.0 as per chart)
10am fc10.0 added 0.4 gal of 10% (target fc 12.0, assuming dichlor might have raised cya to 30)
11am fc 12.0 cya tested at 40ppm; added 1.0 gal of 10% (target fc 16 for cya of 40)

Keeping cover on pool in between additions of 10% to prevent sunshine degradation of CL. Also suspect that some algae may be on the underside of the cover, so trying to expose the cover to high level CL.

1pm fc 16.0 lowered swg to 20%(from 40%)
5pm fc 16.0 no change, no addition
9pm fc 14.0 added 0.5 gal 10% hypochlorite, turned off swg

Day 3
7:30am fc 18 no addition; brushed pool
2 pm fc 13.5 added 0.6 gal of 10% hypochlorite (target fc 16)

Water is sparkling. Will stop if oclt is zero again. (cc 0.5). This is faster and easier than I expected.

 

[DogsHouse_MyPool]

I too am having difficulty keeping CYA in my pool. I am new to the TFPC/BBB this year, so I am not real sure about previous years as I was getting "free testing" at the local PaP. I am going to buy a R-7065 CYA Standard Solution so I can verify my testing procedure.

I am also finding out that testing in the evening is producing inaccurate results, as the color temperature of light is affecting my test results, not just for the the CYA test, but also pH (and probably others to a lesser extent). I will probably get a 6500K daylight light source so I can continue testing in the evening, as I find it most convenient.